This invention relates to an improved apparatus for introducing phase delays to a signal. The invention has application in introducing phase delays to the antenna elements of a phased array antenna and has particular application in radar and communication satellite applications of a phased array antenna.
For various types of electrical apparatus it is necessary to introduce phase shifts in a signal. For instance, in establishing the transission beam pattern of a phased array antenna, it is necessary to deliver the signal to each antenna element with a particular phase delay, referred to an arbitrary standard phase. If a beam pattern similar to the transmission beam pattern is required for reception, a particular phase delay similar to that introduced for transmission must be introduced to the signals received by each antenna element before the received signals are combined.
Where a signal is carried on several lines and it is necessary to phase shift the signal on each line with respect to the other signals, it is usual to have a phase control unit associated with each line. For example, Hannan, in Canadian Pat. No. 1,023,847, issued Jan. 3, 1978 discloses a phase control unit associated with each radiating antenna element of a phased array antenna. Such phase control units may produce continuous or incremental phase shifts; as these units require electronic components they are usually the most expensive part of a phase control system.
It is an object of the present invention to provide a phase control system which is inexpensive when compared with the expense of associating variable control units with each of several signal carrying lines.
For certain applications it is known to connect a matrix between the input and output lines in order to phase shift the signal frequency on the output lines. In operation, a known set of phase shifted signals is selected by applying the input signal to the appropriate input port. Only by applying the signal to different input ports are different "routes" through the matrix selected, and consequently, different phase shifts chosen. See for example Canadian Pat. No. 1,027,670 by Kadak, issued Mar. 3, 1978, in which such a matrix is associated with a phased array antenna.
In order for a phase selecting matrix to operate satisfactorily for certain applications, such as beam steering applications in connection with Time Division Multiple Access (TDMA) communication satellites and certain radar, the matrix must have the following characteristics: frequency response in excess of 1 GHz, switching time of less than 10 ns., transmission band width in excess of 500 MHz, isolation of more than 80 dB and cross talk levels. at least 65 dB below the signal level. The prior art matrices do not have these characteristics.
It is a feature of the present invention to provide a phase selecting switching matrix with these characteristics.
In phased array antenna apparatus it is necessary to supply some device as an "on-off" switch for transmission and reception.
It is a further feature of this invention to utilize the fast switching characteristics of the opto-electronic switching matrix as a transmission or reception gating ("on-off") switch in addition to its use as a phase selector.
The invention relates to apparatus for selecting a set of phase-shifted components of an electrical signal comprising: a plurality of phase shifting means; first signal conveying means coupled to each of the phase shifting means; a plurality of opto-electric transducers arranged in an array; second signal conveying means coupling each phase shifting means to each opto-electric transducer in a corresponding row of the array; and a plurality of lines each connected to the opto-electric transducers in a column of the array whereby the opto-electric transducers when enabled couple signals between the phase shifting means to the lines to provide the set of phase-shifted components.
In another aspect, the invention relates to apparatus for selecting a set of phase-shifted components of an electrical signal comprising: a plurality of signal delay means; first signal conveying means coupling the signal to each of the signal delay means; a plurality of opto-electric transducers arranged in an array; second signal conveying means coupling the output of each signal delay means to each opto-electric transducer in a corresponding row of the array; and a plurality of output lines each connected to the opto-electric transducers in a column of the array whereby the opto-electric transducers when enabled coupled signals from the outputs of the delay lines to the output lines to provide the set of phase-shifted components on the output lines
In another aspect, the invention relates to apparatus for selecting a set of phase-shifted components of an electrical signal comprising: an optical modulator responsive to the electrical signal to provide an intensity modulated optical signal; a plurality of opto-electric transducers arranged in an array; a plurality of optical paths of varying length extending between the output of each modulator and a respective row of opto-electric transducers in the array; and a plurality of output lines each connected to a column of the transducers in the array, whereby the output lines are selectively energized with the set of phase-shifted components.
In yet another aspect, the invention relates to apparatus for selecting a set of phase-shifted components of an electrical signal comprising: a plurality of delay lines adapted to receive the signal; a plurality of optical modulators, one connected at the output of each delay line; a plurality of opto-electric transducers arranged in an array; a plurality of optical paths of equal length extending between each optical modulator and a row of tranducers in the array; and a plurality of output lines each connected to a column of the transducers in the array, whereby the output lines are selectively energized with the set of phase-shifted components.